I'm cross posting this here from one I initially did on another forum since I don't know how much cross traffic there is between the two. Enjoy.

DIY Roundel Guide
by Nadaclue a.k.a. Chad W.

Introduction

Being a person who doesn't like to leave well enough alone, I feel that it's the small details in a car that make it special or unique. One day while sitting in my garage I decided that while the BMW roundel is nice and the BMW name carries some respect with it, that I wanted something different.

Internet searches brought up mainly carbon fiber or *gasp* jewel encrusted roundels. There were also for companies such as ACS, Dinan and other tuners but without the tuner parts I don't feel the car should have tuner badges.

So after a couple days of playing around with some spare roundels (82 mm to be exact) that I bought from ebay, I came up with the following:

This DIY guide is an attempt to help others who may want to do the same.

Step 1: Source your roundels

Depending on how confident you are, you can use the roundels that are currently on your car. This DIY is somewhat destructive, but no "donor" parts are needed. I bought mine off of ebay, or any used roundels will work as long as they aren't dented or deeply scratched. Here is the roundel I started with:

Just a typical 2 pin 82mm roundel that can be used on the trunk or side markers of an E85.

Step 2: Remove the clear coat (or sticker as it is)

So I didn't want to just put some cheesy vinyl sticker over my roundel, which meant I had to find out if I could strip this roundel down to a bare surface for some sort of painting or decal transfer. After a little investigation with an x-acto knife, I learned that the factory roundels are not clear coated with a paint, but rather have a clear sticker over top of them.

With a little persistence and use of the x-acto knife and scraping with the finernail I was able to fully remove the clear sticker.

Now we are left with an unprotected, albeit sticky, BMW roundel. Next we have,

Step 3: Remove the clear sticker residue and factory BMW coloring

Now you'll notice that your roundel is all tacky, this is the residue left over from the clear sticker. Nothing a little solvent won't fix. I have access to an unlimited solvent selection, but I tried to stick with the basics so no one should have trouble. The best off the shelf solution I found was acetone. You can get it at most paint/hardware stores or you can use fingernail polish remover. Here I've begun the wiping down using acetone:

After about 5 more minutes of wiping I'm left with:

That's when it got interesting. I learned three valuable facts; number one is that the roundel is actually 2 pieces, number two was that the inner roundel piece is aluminum, and number 3 is that the BMW logo is stamped into the aluminum disc. Being two pieces with the inner piece being metal made life easier in the long run. The fact that the logo is stamped prove to increase the complexity of the DIY roundel a little bit.

Step 4: Sanding the roundel to remove the stamped logo

In order to proceed the way I had originally planned, I needed to remove the raised portion of the factory roundel or else I'd end up with a ghost image coming through my new roundel. I began this little endeavor at work, and only had 400 grit sandpaper to work with but it ended up working OK, just more time and elbow grease than I thought. When I do this again, I start with 220 grit and then finish it with the 400 grit. The goal here is to removed as much of the raised section as possible. After the first 30 seconds you can see the areas that will be problematic:

After about 25 more minutes of wet sanding, I ended up with this. While you can still see a slight ghost image, the fact that I will be painting the roundel helps here. I will use a sanding primer to build it up slight and then smooth everything out with sandpaper.

Step 5: Separating the two parts of the roundel

In order to be successful, I now needed to separate the aluminum disc from the plastic housing. I put the sanded roundel into a 230F industrial oven (do not use your home oven, the adhesive they used smells noxious and will potentially introduce chemicals into your oven) for 25 minutes. After 25 minutes I used a very flat object, in my case a chemical weighing spatula, to pry the two parts away from each other. I put the flat end at the very edge of the aluminum disc and carefully pried up. Be careful at this point, as the aluminum disc is very thin and easy to distort. Make sure the roundel does not cool before you try to pull it apart, you will bend and distort the disc.

Next I simply had to clean up the adhesive. Again, acetone works fairly well but it is harder to remove than the paint was. Be gentle but persistent and you will get all the residue off.

Step 6: Painting the plastic back half

Now that everything is apart and sanded, it’s time to start laying down some paint. Here are the coatings that I used, all can be purchased from your local parts store as I didn’t use any sort of specialty paints. For the plastic backing half of the roundel, we need to use a plastic adhesion promoter and your color of basecoat. This basecoat will form the visible edge of the roundel:

And my black basecoat:

Step 6.1

Since we’re only really concerned with the outer edge of the roundel and should have gotten sanded when you sanded the aluminum face, there’s no reason to worry about further sanding. Just follow the directions on the spray paints and remember to try and do this in a clean, well ventilated environment. These are solvent based coatings and are flammable as well as contain chemicals that can be harmful if inhaled.

I applied 2 light coats of the adhesion promoter to the plastic, making sure to avoid runs and doing light coats.

Follow the directions for recoat times here, you’ve done all the hard work and you don’t want to have a shoddy looking piece because you rushed it or let it sit to long. With the adhesion promoter there is a very specific window of time when you need to apply your basecoat, make sure to read and then re-read the directions carefully.

Step 6.2

Once I had allowed the minimum amount of time to pass, I put on a light coat of the black basecoat. Again, work in multiple light coats of paint. Don’t worry if you don’t have that high gloss shine the first time around, it’ll develop over multiple coats.

First coat:

And after my third and final coat. You can see much more shine/gloss has developed:

And that’s it for the backing. Again, remember that you can use any color you want here and it’s dependant upon your desired design. I wanted a black trim ring around mine to help set off the colors without being overly bright.

Step 7: Prepping and painting the aluminum front half

Now that the back and ring are painted the color you want, it’s time to move your attention to the front half of the roundel. Again, remember to follow all safety precautions and directions on your paint. The time you’ve put in so far to this project would be wasted if the finished product starts falling apart, and no project is worth damaging your health.

All paint was again sourced from my local auto parts store, nothing fancy or high end here but it gets the job done. For the roundel front we’ll need an etching primer, sanding primer and most likely a white basecoat. More on why you want a white basecoat in a bit.

The etching primer insures a good bond between your paint and the aluminum substrate. Aluminum is difficult to stick to, but the nature of etching primers ensures a good bond and substrate for your sanding primer and basecoat.

The sanding primer is going to allow you to build up the surface of the roundel and help hide that ghost image that we have left. Essentially what it is is a paint with a high solids content that dries very fast. This allows you to build up the primer and sand it down flat and smooth, hiding the raised ghost image.

And finally the basecoat. As I said, you’ll most likely be using a white or other light colored basecoat. I’ll explain why when we get to actually putting the design onto the roundel.

Step 7.1

Begin the painting by ensuring that the aluminum roundel is clean and free of any finger oils or sanding contaminants. Get out that acetone that you used earlier and thoroughly wipe everything down. I highly suggest where rubber gloves at this point. The oils from your hands can make it extremely difficult for the paint to adhere and you may end up with adhesion failures down the road.

As I said, the etching primer is designed to create a substrate that your primer / basecoat can stick to. This coating goes on very thin and is merely there to act as corrosion resistant barrier as well as bite into the aluminum. Two very light mist goes works well, just ensure that you end up with a smooth uniform finish and follow directions for re-coating on the label of the can.

Here you can see what my etch primed roundel looked like. You can see some of the ghost image coming through, but don’t worry as we’ll take care of that next.

Step 7.2

Once your etch primer is properly cured, it’s time to put on the sanding primer. This is a multi step process that helps smooth everything out. First I put down two coats of the sanding primer and made sure I had a nice smooth uniform film.

Then once it was cured per the cans instructions, I sanded it with 400 grit sandpaper. Don’t worry about sanding down to the green etch primer. Just be sure NOT to sand through the etch primer to the metal other wise it’s time to start over.

Repeat the painting / sanding step until you are happy with your results. How much time you initially spent sanding the aluminum down will dictate how many coats of sanding primer you’ll need. The smoother the substrate was to start with, the less primer you’ll need. I ended up with just 2 coats of primer until I was satisfied. Don’t be worried if you see some etch primer still coming through the black. The way we’re going to put on the design will help hide the minimally ghosting that’s still left. As long as it feels relatively smooth to the touch, you’ll be good to go. Here’s my finished results:

Step 7.3

Now for the last bit of painting, the basecoat. Wipe down your sanded roundel with acetone once the primer has fully cured in order to remove any dust that may have remained. Don’t worry if your rag gets a little bit of black transfer, just don’t saturate the part so that the primer begins to soften. If this happens, put the roundel aside for a day and let the coating regain its hardness.

The basecoat is pretty simple and straight forward. Again, be sure to use multiple light coats of paint. We want full color development and we don’t want a grayed out coating. Once you have a smooth finish, let it cure out for a couple of days before continuing. We want to make sure all of the solvents are out of the paint before we begin applying our image. Also, it’s important to have a smooth appearance here with no grit / dirt in your paint otherwise that will show through image. Feel free to wet sand with 1800-2000 grit sandpaper to get it smooth as possible, since I work in a clean environment that wasn’t necessary for me.

And here’s the front of the painted roundel sitting in the black back piece. The black rim will nicely frame out my design later:

So far so good. Now the painting part is done on the roundel and its time to get onto the fun part of the project, picking out your design and seeing the fruits of your labor come together.

Step 8: Remember building models?

And here we go, the final stretch. This is where it all pays off, so take your time! This is the trickiest part of the whole thing, but I personally think it’s the most ingenious.

The big question I had was “How do I get a custom design on the roundel once I have a blank canvas, I’m no artist” and so I thought about it for a while. Then one day I was thinking about something totally unrelated and remembered building model airplanes as a kid and how they had the decals that you put on by soaking them in water and that’s when the idea hit me. Why not just do a big water transfer? With modern photo printers it is easy to generate high quality images, I just had to source the paper and thankfully we live in the wonderful times of the internet.

A quick Google search of “inkjet water decal paper” will lead you to many sources, here is one example http://www.decalpaper.com/product-p/25c.htm . Just to be clear, I am in no way affiliated with that website nor have I personally ordered from them. They’re just an example of someone who has such products. Be sure to buy the right paper for your printer and for your design, they offer paper for inkjet or laser printers and clear or white transfer paper. The paper you choose will be based on your design, the clear paper works best for bright colors like I wanted, just use a white or other bright color basecoat for your roundel. If you want a darker design, I’d suggest the white decal paper.

Step 9: Pick out your design

This part is entirely up to you, and it calls for a little creativity. You want to find high resolution images to use and I suggest Google image search or something similar. You’re going to be printing this out at 3.33” x 3.33” so be sure that the image is large enough and of high enough resolution that it will print cleanly at that size. I HIGHLY suggest doing lots of test prints on regular paper to ensure you get what you want.

Once you have your image, you can resize it and manipulate it in your design program of choice. I suggest something like Photoshop or one of the free photo editors such as GIMP or Irfanview. Once I had an image I was happy with, I pasted it into Microsoft Word so I could print several of them onto one sheet. If your image editor can do that as well that is fine.

For my particular design, I ended up with an image that was 3.33” x 3.33”. This gave me about 1/8” worth of image to wrap around the back side of the roundel. If your image is smaller and doesn’t fully wrap behind (you’ll see what I mean by wrapping behind it shortly), you’ll be able to see whatever your basecoat color was around the edge of your image.

Step 10: Print your image

Be sure and follow the directions that came with your transfer paper. You’ll be printing on the glossy side of the paper, and I suggest setting your printer to its best possible settings and assigning it to glossy photographic paper. Again, the transfer paper you buy will have directions

Here is my image freshly printed on the decal paper:

The next step is important, but it may depend on the type of decal paper you buy. I know for my particular example it was essential. Allow your printed image to fully dry for a couple of hours, then apply several very light coats of clear spray paint. The clear paint “sets” the ink and makes it smudge proof, it also makes the decal paper much more durable and easier to work with once you soak it and remove the backing paper. Without the clear coat, the free decal would tear very easily. Your decal paper instructions should clarify if this step is necessary, but for the intents of this DIY guide I’m saying it is. Here’s a picture of my clear coated decals, notice how much glossier they were than in the previous picture:

Step 11: Time to transfer your decal to your roundel

Here comes the tricky part, getting that image onto the roundel. First cut your image out, making sure to leave excess around the edges so you can more easily manipulate the film once it’s off the backing paper and onto the roundel

For the paper I bought, it was recommended that I soak the trimmed decal in warm water for 45-60 seconds. The decal will start to curl and it should be very simple to slide the image off the backer paper. I simply slid the decal off the paper directly onto the roundel. However you do it, make sure the now free image doesn’t start folding into its self. It becomes very difficult to separate it without tearing it. Just picture pulling off some cling wrap and what happens when it touches its self.

Once you have the image sitting on the roundel, it’s not going to look the best but don’t worry.

Just very slowly manipulate the decal as it dries, working the bubbles out one by one. It should smooth out fairly easily as it begins to dry and the adhesive kicks in. As you can see from my picture I have excess decal over the edge of the roundel. You can choose to cut that off once it’s dried, or you can fold it over the back like I did. You’ll end up having to trim some of it when it comes time to completely re-assemble everything but I found folding it back worked for me. I think that’s a personal preference on how you work it at this point.

I suggest putting the decal in the sunlight once you begin to be happy with how it looks. As it dries down and cures out more, the surface will tighten and more bubbles will disappear. Just try to get as many out as you can while it’s wet.

Here’s mine in the drying stage:

And the fully dried decal:

I would allow this to sit around for 7-10 days to ensure all of the water is out and the adhesive is cured, then apply 2-3 coats of clear coat. If you prefer, you can re-assemble your complete roundel before clear coating, but do not apply too much clear coat as it’ll be visible in the seam where the aluminum disc sits into the plastic backing.

A word to the wise, when re-assembling your roundel practice with it on the car especially if the roundel you’re using has pins on the back. You want to make sure that new image is aligned horizontally, otherwise if you put the aluminum piece back into the plastic backing before you test it on the car your new roundel will likely end up crooked. If the roundel attaches with double sided tape to the car it doesn’t matter. But like I said, if the roundel uses the guide pins make damn sure the aluminum front half ends up being horizontal on the car. You’ve been warned!

And here’s what makes it all worth it, a one of a kind roundel:

And by the way, the BMW roundels aren’t the only thing that this treatment can be done to. I’m in the process of making custom center caps for my newly refinished Breyton Inspirations as well:

To my surprise they came apart and were made exactly like BMW roundels. I don’t know if the OEM BMW center caps are made this way as well, but I don’t think the ones on my Z4 were but in all honesty I never looked that closely.